While the first recorded use of chemicals to control pests dates back to 2500 BC, only in the last 60 years has chemical control has been widely used. Early pesticides included hellebore to control body lice, nicotine to control aphids, and pyrithrin to control a wide variety of insects. Lead arsenate was first used in 1892 as an orchard spray, while at the same time it was discovered that a mixture of lime and copper sulphate (Bordeaux mixture) controlled downy mildew, a fungal disease of grapes.
The modern era of chemical pest control commenced during World War II. For example, DDT played a major role in maintaining the health and welfare of soldiers who used it to control body lice and mosquitoes. Further developments of pesticides followed, and with their relatively low cost, ease of use, and effectiveness, they became the primary means of pest control. Protection of crops, produce, animals, and humans over extended periods became possible with corresponding increases in food production and improved standards of living.
Some modern pesticides are sophisticated compounds that are carefully researched to ensure they are effective against target organisms, generally safe to the environment, and can be used without undue hazard to users or consumers. Many of these have been developed to target specific biochemical reactions within the target organism, e.g. an enzyme necessary for photosynthesis within a plant or a hormone required for normal development in an insect. Thus, some modern chemicals are safer, more specific, and friendlier to the environment than the older products they have replaced.
Furthermore, G protein-coupled receptors (GPCRs) form one of the largest families of integral membrane receptors. GPCRs transduce information provided by extracellular stimuli into intracellular second messengers via their coupling to heterotrimeric G proteins and the subsequent regulation of a variety of effector systems. Therapeutic agents often target GPCRs because of their capability to bind ligands, hormones, and drugs with high specificity. Agonist activation of GPCRs also initiates processes that desensitize GPCR responsiveness and their internalization.
Common to most GPCRs is the cyclic process of signaling, desensitization, internalization, resensitization, and recycling to the plasma membrane. This cycle prevents cells from undergoing excessive receptor stimulation or periods of prolonged inactivity. Mechanisms for desensitization of GPCRs include receptor phosphorylation and subsequent endocytosis, which removes the receptor-ligand complex from the cell surface. As a result of this desensitization process, a common limitation of GPCR-targeted compositions is target organism tolerance or resistance, as receptor desensitization can mute their effectiveness.